Marine Surface Effect Ships (SES) in their generic form have a upper hull that is rather flat on its underside with downward extending asymmetrical catamaran sidehull portions either side. These asymmetrical sidehull portions are connected transversely fore and aft by flexible seals. The boundary of the space thus formed is pressurized with air supplied by powered blowers to thereby form a deep air layer between the hull and the water's surface. This results in a vessel that has little water contact and is therefore quite efficient at high speeds in calm water.
Major shortcomings of the generic SES are that: 1) The wide barn door effect of the flexible bow seal contributes to a drastic increase in resistance and poor sea keeping characteristics when moderate to high seas are encountered, 2) The flexible bow seal allows waves to enter and upset the stability of the supporting gas cushion that is really a huge gas spring. This results in a very uncomfortable 2–4 cycle per second oscillation that is commonly known as the SES “cobblestone” ride effect, and 3) The large full span flexible bow and stern seals are rather expensive and high maintenance.
Applicant has successfully addressed the shortcomings of the generic SES with his patented SEACOASTER SECAT (Surface Effect CATamaran) inventions. SEACOASTER has fine entry bows on long and slender sidehulls with gas cushion recesses built into their undersides. Blower pressurized air is supplied to the two recesses thereby essentially forming two parallel surface effect ships mounted to a common hull structure. The shortcomings of the generic SES are avoided since there are no high cost and maintenance flexible seals and there is no gas cushion between the sidehulls. The fine entry bows of the SEACOASTER's sidehulls provide an excellent ride in rough seas and there is no “cobblestone” ride as is experienced with the generic SES.
However, compared to a generic SES of similar size, the SEACOASTER inventive hull has two shortcomings: 1) It has about 30 percent less air cushion surface area and hence requires a higher cushion pressure due to the non-pressurized area between its sidehulls and 2) It has more wetted area since it has four sidewalls, one on each side of each of its air cushions, while the generic SES has only two sidewalls. Even with these relatively minor shortcomings, the SEACOASTER is proving to be a very successful concept due to its high efficiency compared to conventional hull forms such as monohulls and catamarans and its shallow draft, excellent seakeeping, and stability.
The instant invention proposed herein addresses the minor shortcomings of the SEACOASTER concept while still designing out the major shortcomings of the generic SES. This will be understood upon review of the following sections.